Optical communication apparatus and optical add/drop apparatus

Abstract

The present invention relates to an optical communication apparatus for detecting the intensity of light in an optical modulator or the intensity of a modulation signal and for controlling the operating point of the optical modulator based on the result of detection. In the optical communication apparatus having such a configuration, the operating point of the optical modulator can be kept stable even when the input light or the modulation signal is temporarily non-existent in the optical communication apparatus.

1. An optical communication apparatus comprising:
 a first optical branching unit branching input light entered to an input port into first and second branched input lights; 
 an optical modulating unit modulating the first branched input light in accordance with a modulation signal to be transmitted, to thereby output a modulated optical signal; 
 an optical detecting unit detecting a light intensity of the second branched input light; 
 a second optical branching unit branching the modulated optical signal output from said optical modulating unit into first and second branched optical signals, and outputting the first branched optical signal to an output port; 
 an operating point controlling unit controlling said optical modulating unit in accordance with the second branched optical signal; and 
 a controlling unit stopping an operation of said operating point controlling unit when the detected light intensity is equal to or lower than a predetermined value, and controlling an operation of said operating point controlling unit when the detected light intensity becomes higher than the predetermined value from a value equal to or lower than the predetermined value. 
 
   
   
     2. An optical communication apparatus according to  claim 1 , further comprising:
 a modulation signal detecting unit detecting a signal intensity of said modulation signal; 
 an optical attenuating unit, connected either between said first optical branching unit and said optical modulating unit or between said optical modulating unit and said second optical branching unit, transmitting or attenuating input light; and 
 an attenuating amount controlling unit controlling said optical attenuating unit in accordance with said signal intensity detected by said modulation signal detecting unit. 
 
   
   
     3. An optical communication apparatus according to  claim 2 , wherein said attenuating amount controlling unit is controlled in accordance with said light intensity detected by said optical detecting unit and said signal intensity detected by said modulation signal detecting unit. 
   
   
     4. An optical communication apparatus comprising:
 an optical modulating unit modulating input light entered to an input port in accordance with a modulation signal to be transmitted, to thereby output a modulated optical signal; 
 an optical branching unit branching the modulated optical signal into first, second and third branched optical signals, and outputting the first branched optical signal to an output port; 
 an optical detecting unit detecting a light intensity of the second branched optical signal; 
 an operating point controlling unit controlling said optical modulating unit in accordance with the third branched optical signal; and 
 a controlling unit maintaining an operating point of said operating point controlling unit when the detected light intensity is equal to or lower than a predetermined value, and controlling an operation of said operating point controlling unit from a maintained operating point when the detected light intensity becomes higher than the predetermined value from a value equal to or lower than the determined value. 
 
   
   
     5. An optical communication apparatus according to  claim 4 , wherein said controlling unit controls said operating point of said operating point controlling unit to a predetermined value in a control range in accordance with the detected light intensity. 
   
   
     6. An optical communication apparatus according to any one of  claims 1  or  2 , wherein an optical attenuating unit transmitting or attenuating input light in accordance with an intensity of said input light is inserted into an input or an output of said optical modulating unit. 
   
   
     7. An optical communication apparatus according to any one of  claims 1  or  2 , wherein said optical modulating unit is controlled in accordance with a signal intensity of said modulation signal or an intensity of input light. 
   
   
     8. An optical communication apparatus according to  claim 1  or  4 , further comprising:
 a modulation signal detecting unit detecting a signal intensity of said modulation signal; and 
 a modulation controlling unit controlling the optical modulating unit in accordance with said signal intensity detected by said modulation signal detecting unit. 
 
   
   
     9. An optical communication apparatus according to  claim 8 , wherein said optical modulating unit is controlled in accordance with said light intensity detected by said optical detecting unit and said signal intensity detected by said modulation signal detecting unit. 
   
   
     10. An optical branching/inserting apparatus comprising:
 a branching/inserting unit connected to a transmission path which transmits a wavelength-multiplexed optical signal, said branching/inserting unit capable of branching and inserting an optical signal with at least one wavelength with respect to an optical signal on said transmission path; 
 an optical wavelength branching unit processing reception of an optical signal branched by said branching/inserting unit for every wavelength; and 
 an optical inserting unit outputting insertion light to be inserted to an optical signal on said transmission path to said branching/inserting unit, 
 wherein said optical inserting unit is the optical communication apparatus according to any one of  claims 1  or  4 .